Coordinate reference system
A coordinate reference system or coordinate reference system (KBS). coordinate reference system , internationally abbreviated as CRS , is a coordinate system that is related to the real world by being linked to a datum. To describe the Earth is Geodetic Datum or Vertical date used.
The term was introduced and defined in the ISO 19111 Geographic Information - Spatial referencing by coordinates standard.
Types of coordinate reference systems
The following types of coordinate reference systems are essentially distinguished:
Geographic CRS
The geographic CRS uses an ellipsoidal model of the earth to describe the position of an object on its surface with two-dimensional coordinates (longitude and latitude). The position of the artificial ellipsoid in relation to the real earth is described with a geodetic datum .
If a height is also specified that is related to the ellipsoid, this is referred to as a 3D geographic CRS .
Geocentric CRS
The geocentric CRS is based on the center of gravity of the earth as the zero point and uses three-dimensional coordinates to describe the position of an object.
Geodetic CRS
Geographical and Geocentric CRS are also known as Geodetic CRS .
More CRS
- Projected: is a geographic CRS in which the coordinates have been projected into the plane through a map projection .
- Local: a CRS that is only used in a local context; for example for construction work or to determine coordinates relative to moving objects (such as ships or aircraft).
- Combined: CRS in which the position and the height are determined in different reference systems.
Differentiation from spatial reference system
The standard ISO 19112 Spatial referencing by geographic identifiers distinguishes the terms coordinate reference system and spatial reference system (ger .: spatial reference system - SRS). In contrast to coordinate reference systems (CRS), where coordinates establish the referencing, spatial reference systems (SRS) use geographic or semantic identifiers for this purpose. This can be, for example, postal addresses or very general information such as “on Alexanderplatz in Berlin” or “east of the Zugspitze”.
EPSG code
→ Main article EPSG codes
EPSG codes are a widely used means of clearly indicating the spatial relationship of spatial data . The 4- to 5-digit key numbers each contain a complete description of a coordinate reference system. There are several hundred such reference systems, and each consists of a list of 10 to 20 parameters. They are described in the list of EPSG codes. Thanks to the short key number, these complex relationships can be exchanged internationally in a simple form.
literature
- ISO 19111: 2007 Geographic information - Spatial referencing by coordinates . Retrieved September 2, 2014.
Web links
- Technical guideline for the Federal Georeference Data Act - TR BGeoRG ( BAnz AT 07.03.2018 B1 )
- Working Group of the Land Surveying Administrations - Geodetic Basics
- CRS-EU - European Coordinate Reference Systems (BKG)
- European Petroleum Survey Group (EPSG) Collection of common coordinate reference systems
Individual evidence
- ↑ ISO 19112: 2003 . Geographic information - Spatial referencing by geographic identifiers.